The present invention relates generally to alinement methods and apparatus, and more particularly to a method and apparatus to aid in the provision of a plane surface which is parallel to a reference plane for installation of rotating ordnance equipment on the deck of a ship.
Alinement procedures may be divided into two separate types: the procedures for alining the ordnance element within itself and the procedures for system alinement, i.e., alining a group of elements or equipment comprising an ordnance installation with each other. It is noted that the principles and procedures explained in this application are applicable to any group of weapons and control equipment. Thus, the general terms "element" or "equipment" are used extensively to designate the individual components of an installation and may mean a gun director, gun mount, turret, rocket launcher, shock platform, radar, gyro compass, or other unit of ordnance equipment.
The alinement of an ordnance element within itself consists principally of steps taken to insure that the element is constructed accurately and adjusted so that its movements are smooth and precise and that, by itself, the element functions as intended. This type of alinement is largely a matter of manufacture and installation and seldom requires adjustment except to correct for tampering, damage and wear.
System alinement consists of the procedures for orienting and adjusting to each other the several elements that constitute a fire control system or battery so that the system as a whole functions properly. These procedures in a first case, refer to the adjustment of the elements so that all associated weapon bores, sight telescopes, radar antennas and other similar lines are parallel (when no parallax or ballistic corrections have been made) and remain parallel throughout their operating motions. These procedures also refer to the adjustment of their related dials of the elements so that they read correctly with respect to established references and the adjustment of synchros which transmit and receive the correct angles. System alinement, as explained in the former case, is the subject with which this application is broadly and mainly concerned.
An important concept in the principles of alinement procedures with respect to ordnance elements is that of the reference plane. The plane in which train angles are measured and normal to which elevation angles are measured, in a two-axis element, is various referred to as "battery reference plane", "deck plane" or simply "reference plane". All of these terms means the same thing, i.e., an arbitrarily selected plane, approximately parallel to the deck, with which train roller paths of all the elements are made parallel to insure that all the elements are parallel to each other. The selected plane may be the actual roller path plane of one of the elements, which one would be governed solely by convenience. It may be a leveling plate set well down in the hull where hull distortion is a minimum, or an imaginary plane without tangible embodiment whatsoever, an example of which is the frequently used "mean plane" or "resultant plane".
Accuracy of fire, which is dependent to a marked degree upon the accuracy of alinement between elements, is thus not dependent at all upon whether or not the reference plane and element roller paths are meticulously alined with any ship structure. It is important only that the planes of the elements be parallel to each other. Of course, extreme misalinement of ordnance elements with the structure of the ship would adversely affect ship stability, but such misalinement would have to be greatly in excess of any reasonably acceptable misalinement between elements before the effect would be perceptible.
Before the elements of an installation are initially installed aboard ship, the element foundations are carefully machined so that the roller path planes are parallel to each other within prescribed limits. Under practical conditions it is impossible to make the planes perfectly parallel. The accuracy with which the element foundations must be machined to parallelism depends upon whether shims, leveling rings, or other alinement refining devices, such as shown in U.S. Pat. No. 4,031,838, issued to Schmidt et al, may be used when the elements are installed. In general, however, alinement refining after installation is possible for the lighter elements only. In the case of heavy elements such as large gun directors, gun mounts and turrets, the desired degrees of parallelism must be attained in the foundation machining operations. This aspect of the prior art tends to make installation costs exceedingly high.
A requirement thus exists for an alinement procedure which eases installation labors, is economical and insures the accuracy of an installation requiring parallelism to a reference plane.